Predicting benefit of radium 223 based on biochemical response and site of metastasis: A real life multicenter UK study.

Abstract

e17034 Background: Studies have shown an improvement in overall survival (OS) and symptom control in metastatic castration-resistant prostate cancer (mCRPC) with Radium-223 treatment. However, there is little information about predicting outcomes using either PSA or Alkaline Phosphatase (ALP) response or comparing bone only disease to bone and lymph node (LN) involvement. Methods: 335 patients receiving Radium 223 at 6 UK centres between March 2014 and June 2020 were included. The primary endpoint was overall survival, secondary endpoints were toxicity, symptomatic benefit and skeletal-related events(SRE) Results: The median age was 75, with 71% having bone only metastases and 29% also having lymph node involvement. Those with PSA response (30%) had a statistically significant improvement in OS, compared to non-responders (18.2 vs 13.8 months, p = 0.026). They also showed highest rate of imaging response/stable disease (54% vs 34%). ALP response was seen in 82%. This did not translate to significantly improved OS, but did correlate with better symptomatic benefit (40% vs 29%). Those with bone only disease showed a survival benefit compared to those with LN involvement (19.4 vs 11.4 months, p = 0.046). Other than anaemia (23.5%), Grade 2 or above toxicities were uncommon including thrombocytopenia and neutropenia(5.5 and 6.2% respectively ) . 14% patients required at-least one blood transfusion. SRE were seen in 24% overall, but lower of in PSA responders(18%). Conclusions: Real life multicentre data suggests that PSA response and bone only disease could be predictors for better survival following Radium-223, whereas ALP response correlates better with symptomatic benefit.